Ignoring the most important part, which airline flies from your hub to where you need to go (in the most circuitous route using the most segments and minimum mileage guarantees all on the cheapest fare available in the market place)...

IMHO, Delta and AA offer the better programs for your use, actually delta may be the number one.

Upgrades: with the 30K annually you get 3 bundles of upgrade certs, 1 (at 20K) giving 2 systemwides (or is it 1?), this compares favorably to both aa and ua which i believe will give you 3 4 packs of 500 mile upgrades for your troubles (and UA's seem to be a hassle to even get once earned-and then a FA will be in your upgrade seat).

Alliance: I put Delta and AA ahead of UA because my opinion of the star alliance on a strictly benefit basis is really low, as an elite, you get no elite bonuses (25% at your level, more of a difference if you have 100% bonus) on partners, whereas AA's oneworld and Delta's AF partnership (alliance with no name) does, with Delta's upgrade certs useable on several partners, and you never know when you may take your partner on a romantic cheap upgradeable mileage earning partner airline flight....

But, I think all will agree, you need to see what works best with your home base and destinations, if half your flights go to an airport not served by DL, then DL is out of consideration, etc.

And I guess if CO is banned, they won't let you get on NW either?? That way at least you could keep your program unchanged.

tg